The prior art may be exemplified by the applicant's prior U.S. Pat. No. 3,912,294 and art cited therein. The present invention provides in a very compact structure a combination of resilient hydraulic mechanical means applying downward forces to tag axle wheels with solid hydraulic means adjustable to set the maximum downward position of the tag axle wheels. The arrangement is such as to provide a maximum articulation of the tag axle, yet with virtually perpendicular force application to the axle-supporting torque beam.
Other prior art has had the tag axle supported at one end of the leaf springs, the other ends of which are pivotally mounted onto the frame, with a two-way hydraulic piston connected intermediate the spring ends. This arrangement does not afford as firmly-acting a suspension, as there is no solid lifting force applied to the wheels, and no solid torque arms to prevent axle chatter and brake hop. The height of the wheels cannot be accurately set in that construction.